The launch of the Fitbit Charge 3 brings obvious questions. How does it compare to the Fitbit Charge 2? When does it go on sale? Fresh from a pre-launch briefing from Fitbit, we attempt to provide some answers.

Fitbit Charge 3 vs Charge 2: the big differences

What’s the difference between the Charge 2 (left) and the Charge 3?

By far the biggest difference is that the Fitbit Charge 3 is waterproof. Expect to see a lot of images of people swimming with the Charge 3 in the coming months.

But it also inherits several improvements from Fitbit’s Versa smartwatch, released earlier this year. These include female health tracking and a SpO2 sensor, which measures the level of oxygen in your blood.

We’ve summarised the key differences below, but note the lack of GPS. If you want accurate tracking on runs, you’ll still need to take your phone with you. The plus side is battery life, with the Charge 3 promising a full week between charges.

Fitbit Charge 3 vs Charge 2: design changes

Fitbit claims the Charge 3 (right) is 20% lighter than the Charge 2

Fitbit tells us that the Charge 3 is “20% lighter and much slimmer” than the Charge 2. We haven’t had a chance to get our hands on samples yet – we hope to at the trade show IFA next week – but it’s clear from the early photos where the changes have been made. The Charge 2’s sensor sticks out from the bottom of the unit, and the design looks more like a watch. We suspect this will fit much more naturally on the wrist.

Fitbit is going heavy on accessories as well. You can buy woven bands for £29.99, and it’s now easier to swap straps thanks to a simple button on either side of the unit.

Fitbit Charge 3 vs Charge 2: on-screen changes

Fitbit also wants to make the Charge 3 more “fun”. You may well wonder what that means in a fitness watch, and here that translates into more animated screens – so hit a target and a chequered flag appears, with firework-style animations for added emphasis. The screen is still mono, but Fitbit claims that it’s introduced more shades of grey too. Try not to get too excited.

Of more interest to runners or those trying to hit fitness targets are the goal-based exercises introduced with the Fitbit Charge 3. These could be calorie-based, distance-based or simply the amount of time you’re exercising. It’s a nice feature that I used to use all the time on my TomTom watch.

Another nice improvement is “run detect with auto stop”, so if you have to wait for the green man to appear before crossing the road it won’t penalise your average pace.

The final thing to note is that tiny REPLY button in the fourth image from the left. Press it and, on Android phones, you can send a quick reply from one of the pre-selected messages. Not quite Dick Tracy, but useful. (iPhone support will follow.)

Fitbit Charge 3 vs Charge 2: greater insights?

The Fitbit Charge 3 (right) includes a SpO2 sensor to measure oxygen levels in your blood

Fitbit is always keen on giving its users genuinely useful information rather than just gathering, say, sleep times and leaving it at that. With the Fitbit Charge 3, that SpO2 sensor for measuring oxygen levels can be used to detect sleep apnoea problems. It won’t solve such health issues on its own, but it does give you something measurable to tell your GP.

Likewise, it will tell you if your resting heart rate has been higher than normal over the past week. As it knows how much sleep you’ve had, it could suggest you look at what time you’re going to sleep. Potentially annoying? Sure. Potentially useful? Definitely.

Fitbit Charge 3 vs Charge 2: which should you buy?

I haven’t tried the Charge 3 yet, so don’t know if it has a potentially annoying flaw. For instance, does the new button design (which is inductive to ensure it’s waterproof) prove annoying in practice? How comfortable is it on the wrist? Fitbit has promised me a review unit when they become available, so I’ll update this article then.

There are two other factors to consider. First is that prices of the Charge 2 may well drop below £100 in light of the Charge 3’s announcement; second is that the Charge 3 isn’t actually available until October.

Personally, I’d wait for the Charge 3. Its waterproofing is the biggest factor in its favour, but I suspect it will also be more comfortable. Once I know more, I’ll let you know. And if you have any other questions in the meantime, make a comment in the field below.